Pageflipping bugs in drm-next on at least Ironlake and Ivybridge.

[Mario Kleiner]

On 07/06/2016 03:05 PM, Chris Wilson wrote:
> On Wed, Jul 06, 2016 at 12:17:55PM +0200, Mario Kleiner wrote:
>> Since i pulled the current drm-next tree i see strong flicker and
>> visual corruption during pageflipping, both in my own app, but also
>> in KDE4 and KDE5 Plasma with desktop composition enabled. This
>> happens on both Intel HD Ironake mobile (Apple MBP 2010) and HD-4000
>> Ivybridge mobile (Apple macMini 2012).
>>
>> It looks like page flips are not waiting properly for rendering to
>> complete, showing partially rendered frames at flip time.
>>
>> If i revert Daniel's commit that switches legacy pageflips from the
>> old code path to the atomic code, all problems disappear, so
>> apparently the atomic code for Intel is not quite ready at least on
>> those parts?
>
> Exactly right, we've reverted the enabling patch for the time being.
> Daniel Stone has spotted the likely problem, but we also want to review
> the handling of state/old_state to see if the same problem has cropped
> up elsewhere.
> -Chris
>

Ah ok, now i see it in drm-intel-next-queued. I'm probably not adding 
anything new here, but wrt. your crc based tests not catching it, while 
it happens all the time for me under KDE, in my own fullscreen app, it 
only obviously happens for some tests, the more graphics heavy ones not 
others, so probably (gfx-)load dependent? Maybe the tests don't put 
enough work onto the gpu to still keep it rendering at flip time.

-mario